Dialysis machines are used to cleanse the blood of medical patients suffering from kidney disease. A dialysis machine includes a blood pump and a blood filter (e.g., dialyzer) through which the blood flows to clean the blood. Arterial blood is drawn from the patient and delivered to the dialysis machine through external tubing. The arterial blood passes through the blood filter, and filtered blood is returned to the patient's venous system through other external tubing. The blood filter is provided with a measured amount of dialysate fluid via a separate dialysate fluid circuit. The dialysate fluid and the blood are separated by a membrane of the blood filter that allows the blood to be cleansed by the dialysate.
As part of the purification process, the dialysis machine incorporates a dialysate filtering system, which can be used to achieve ultrapure dialysate. After each treatment, the dialysate filtering unit is typically rinsed with purified water, which may be heated and may also include cleaning agents during part of the rinse cycle. It is also typically cleaned with a chlorine bleach solution about once per week, or sooner if the dialysis machine has not been used in more than about forty-eight hours. The water source and the bleach solution source are connected to the dialysate fluid circuit. The dialysate fluid circuit also includes a drain tube that empties spent fluid to a facility drain outside the dialysis machine.